Gerotor pumps are commonly used in power transfer assembly of the type installed in motor vehicles for supplying lubrication to the rotary components as well as for cooling torque transfer assemblies such as, for example, multi-plate friction clutches. Such power transfer assemblies include manual and automatic transmissions, transaxles, power take-off units, all-wheel drive couplings and four-wheel drive transfer cases. Typically, the gerotor pump has an outer ring defining a pumping chamber and an inner ring that is positioned in the pumping chamber and which is fixed for rotation with a driven member (i.e., a shaft, etc.). The inner ring has external lobes which are meshed with, and eccentrically offset, from internal lobes formed on the outer ring. Because the number of internal lobes is greater than the number of external lobes, driven rotation of the inner ring results in a pumping action such that a supply of hydraulic fluid is drawn from a sump in the power transfer assembly into the suction side of the pumping chamber and is discharged from the pressure side of the pumping chamber at an increased pressure.
Traditionally, the gerotor pump is continuously driven regardless of the lubrication and/or cooling needs. In addition, as the rotational speed of the driven member increases, the pressure generated by the gerotor pump correspondingly increases. As a result, additional energy is used to drive the pump, thereby reducing the overall efficiency of the power transfer assembly.